10 Nov 2011 ... Electron accelerators in the range 10 – 25 MeV in most cases are also built as RF
linear accelerator with max beam power up to tens kW and ...
LOW ENERGY ELECTRON ACCELERATORS APPLICATION V. Shvedunov Skobeltsyn Institute of Nuclear Physics Lomonosov Moscow State University 10 November 2011
Electron accelerators in the range 0.5 – 100 MeV Some applications use bremsstrahlung (X-rays) radiation, some – electron beam. For X-rays
I = I 0 exp(− µx ) For electrons
Different mechanisms of radiation interaction with matter are used for different applications - at level of molecules, atoms, nuclei
ACCELERATORS
Electron accelerators in the range 0.5 – 5 MeV in most cases are built as direct current accelerator with max beam power up to several hundred kW and efficiency 80-90%.
Basic suppliers: Nissin High Voltage Ion Beam applications Budker Institute Efremov Institute
Examples of electron accelerators in the range 0.5 – 5 MeV
Nissin HV 5 MeV,150 kW ELV (Budker Institute) 0.2 – 2.5 MeV, up to 500 kW
Examples of electron accelerators in the range 0.5 – 5 MeV DYNAMITRON (IBA)
Electron accelerators in the range 5 – 10 MeV in most cases are built as RF standing wave or traveling wave linear accelerator (linac) with max beam power up to hundred kW and efficiency 20-30%.
Traveling Wave (TW) RF waveguide Standing Wave (SW)
CUT VIEW OF STANDING WAVE ACCELERATING STRUCTURES
Side coupled
On-axis coupled
Examples of electron linacs in the range 5 – 10 MeV
TitanBeta SW linac 10 MeV, 25 kW Mitsubishi Heavy Industries TW linac 10 MeV, 25 kW
IMPELA SW linac 10 MeV, 50 kW
SureBeam SW linac 5 MeV,100 kW
Example of electron accelerator in the range 5 – 10 MeV - recirculating RF cavity accelerator
Rhodotron, IBA 5 -10 MeV up to 700 kW
In some applications cheap betatrons are used in the range 3 – 25 MeV
Betatron principle
10 MeV betatron for IORT (Tomsk)
3-7.5 MeV betatrons (Tomsk)
Electron accelerators in the range 10 – 25 MeV in most cases are also built as RF linear accelerator with max beam power up to tens kW and efficiency 20-30%. In some cases microtrons and betatrons are used.
Microtron
Examples of electron accelerators in the range 10 – 25 MeV
MEVEX, Canada, 35 MeV linac for isotopes production
Varian 25 MeV Clinac
20 MeV circular microtron, Indore, India
Electron accelerators in the range 25 – 100 MeV in most cases are built as multisections RF linear accelerator or as race-track microtron (RTM).
Examples of electron accelerators in the range 25 - 100 MeV
Scanditronix medical RTM MM-50
Danfysik 53 MeV RTM
Research Instruments 100 MeV linac
APPLICATIONS
Electron accelerators application for material processing, sterilization, desinsection Chemical and biological effects at molecules level are produces by ~eV energy electrons. Initial high electrons energy is required to penetrate inside the material. Productivity:
∆m Pbeam =η ∆t D
To increase penetration electron energy can be converted to X-rays energy at bremsstrahlung target, but efficiency of conversion in energy range below 10 MeV is below 10%, so high power electron beams are required.
Dose requirements for various radiation effects and productivity for 10 kW electron beam power 1 Gy = 1 J/kg •
Radiation effect
Dose requirements
Productivity
•
Sprout inhibition (potatoes, onions)
100-200 Gy
~200-100 tons/hour
•
Insect control (grains, fruits)
250-500 Gy
~80-40 tons/hour
•
Fungi and mould control
1-3 kGy
~10-3 tons/hour
•
Bacterial spore sterilization
10-30 kGy
~2-0.7 tons/hour
•
Polymerization of monomers
10-50 kGy
~2-0.4 tons/hour
•
Anthrax killing
50-100 kGy
~400-200 kg/hour
•
Modification of polymers
50-250 kGy
~400-80 kg/hour
•
Degradation of cellulose materials
100-500 kGy
~200-40 kg/hour
•
Topaz coloring
10-200 MGy
~1-0.05 kg/hour
Irradiation facility based on “Dynamitron” (IBA)
Rated Voltage
Rated beam current
550 keV
70/100/160 mA
800 keV
70/100/160 mA
1 MeV
60/100 mA
1.5 MeV
40/65 mA
2.5 MeV
40 mA
3 MeV
34/50 mA
4.5 MeV
20/34 mA
5 MeV
10/20/34 mA
Structure of 10 MeV/25 kW irradiation facility
http://www.mhi.co.jp/hmw/melbis/structure-e.html
SINP MSU experience in design, construction and application of electron accelerators for radiation technologies
SINP MSU 60 KW, 1.2 MEV COMPACT CW LINAC FOR RADIATION TECHNOLOGIES
OneSection
TwoSections
Beam energy
0.6 MeV
1.2 MeV
Beam current
0 to 50 mA
0 to 50 mA
Maximum beam power
30 kW
60 kW
Length
0.8 m
1.3 m
Gun/klystron high voltage
15 kV
15 kV
Plug power consumption
~75 kW
~150 kW
Electrical efficiency
~40%
~40%
SOME CURRENT APPLICATIONS OF 1.2 MEV COMPACT CW LINAC 1. Test of spacecraft elements (solar batteries etc) for radiation effects 2. Source of high dose rate X-rays radiation 3. R&D for radiation technologies
Thermo shrinkable polyethylene film dimensions decrease after different doses. Optimal dose 120 kGy.
Intensive bremsstrahlung X-rays source (30 Gy/s at average energy 300 keV)
SINP MSU COMPACT CW LINEAR ACCELERATOR FOR RADIATION TECHNOLOGIES WITH LOCAL RADIATION SHIELDING CWL-1-25 Under construction. Beam energy Average beam current Average beam power Operating frequency Klystron average power Wall plug efficiency Beam scanning width Accelerator dimensions
1 MeV 25 mA 25 kW 2450 MHz 50 kW 30% 80 cm 470 x 784 x 1375 mm1)
1)Without output horn and power supply
Accelerator is able to provide operation of thermo shrinkable polyethylene film facility with productivity up to 10000 tons/year
SINP MSU 10 MeV TECHNOLOGICAL LINAC
Beam energy Pulsed beam current Average beam power Operating frequency Klystron pulsed power Klystron average power Wall plug efficiency Beam scanning width
10 MeV 430 mA 15 kW 2856 MHz 6 MW 25 kW 20% 80 cm
Energy spectrum, beam image and beam profile
0.08 0.07 0.06
0.04 0.03 0.02 0.01
180 160
0 -0.01
140
0
2
4
6
8
10
12
120 100
E (МэВ)
I
I(45)/I(0)
0.05
80 60 40 20 0 -3
-2
-1
0 y (mm)
1
2
3
SOME CURRENT APPLICATIONS OF 10 MEV LINAC
1. Test of spacecraft elements (solar batteries etc) for radiation effects 2. R&D for radiation technologies
Example of possible application – gemstones colorization
SINP MSU 10 MeV TECHNOLOGICAL LINAC Proposal
Pulsed Linear Accelerator PLA-10-15H Beam energy Pulsed beam current Average beam power Operating frequency Klystron pulsed power Klystron average power Wall plug efficiency Beam scanning width Accelerator dimensions 1)Without
output horn and power supply
Pulsed Linear Accelerator PLA-10-15V 10 MeV 430 mA 15 kW 2856 MHz 6 MW 25 kW 20% 80 cm 470 x 784 x 1375 mm1)
CARGO INSPECTION AND RADIOGRAPHY X-rays produced by electrons at bremsstrahlung target are used in both applications. X-rays are attenuated by inspected object and registered by X-rays detectors or by film.
Basic processes responsible for X-rays attenuation
Cargo inspection. 40 mln. sea containers per year move in the word.
Cargo inspection - goals. 1. Detection of contraband. 2. Detection of fissile and radioactive materials. 3. Detection of explosive and drugs. Different approaches are necessary for each problem, but in all cases electron accelerators are used or can be used.
Typical dimensions.
Required speed of development: 0.5 m/s
Main components of cargo inspection complex
Basic companies providing equipment and complexes for cargo inspection are: Varian Medical Systems (USA) Smiths Detection (UK) Nuctech (China) L-3 (USA) Rapiscan (USA) SAIC (USA) AS&E (USA) ………….. Several other companies are working in this direction
Single energy bremsstrahlung X-rays do not permit to evaluate atomic number and can produce only gray picture 10.00
Bremsstrahlung spectrum
1.00
2
µ/ρ (cm /g)
Uranium
Iron
Co 60
0.10 Nitrogen
0.01 0.1
1.0 E (MeV)
10.0
Dual energy bremsstrahlung X-rays do permit to evaluate atomic number and can produce color picture 10.00
Bremsstrahlung spectra
1.00
2
µ/ρ (cm /g)
Uranium
Iron 0.10 Nitrogen
0.01 0.1
1.0 E (MeV)
10.0
The most widely used are X-ray sources from Varian Medical Systems. Linatron-Mi –is dual energy X-Ray source fed by magnetron
Nuctech (China) – also produces 6/9 MeV dual energy X-Ray source fed by magnetron
Design by SINP MSU team of 3/6 MeV linac with interlaced energies for cargo inspection X-rays head
Beam energy Dose rate at 1 m Operating frequency Pulse repetition frequency Accelerator dimensions Accelerator weignt 1)Including
Control console
local radiation shielding
3.5/6 MeV 0.2 – 2 Gy/min 2856 MHz 50 – 400 Hz 1000x600x900 mm 900 kg1)
Energy spectrum in interlaced energies mode 600 500
Iav (nA)
400 300 200 100 0 0
1
2
3
4
5
6
7
8
E (MeV)
Low
High
Beam spots diameters are well below 2 mm
Scale: 1 square= 1 1 mm
ACCELERATOR WITH FAST MAGNETIC ENERGY SWITCHING FOR CARGO INSPECTION (PROPOSAL)
RTM Parameters Beam energies
3.5, 6, 9 MeV
Operating frequency
2998 MHz
End magnets field
0.63 T
Injection energy
25 keV
Pulsed RF power
39Ca + n
+ γ --> 207Pb + n
Photo activation technique –method of elemental analysis – using photonuclear reactions.
Nuclei level structure is unique fingerprints permitting to detect specific elements in very low quantities Level structure of gold isotope 196Au. Level with energy 595.66 keV has half life period 9.6 h. 196Au
can be produced in this isomeric state via photoneutron reaction at stable isotope 197Au. In this way gold content in ore can be defined with high sensitivity - better than 1 g/ton
Photo activation technique
Photo activation technique
Gamma ray spectrum obtained with Ge detector
Accelerators for photo activation technique Electron beam parameters: Beam energy from ~ 10 MeV to ~30 MeV Beam average current from ~100 µA-1 mA Conversion to bremsstrahlung X-rays
Isotopes production Most isotopes for medicine are produced now with cyclotrons, proton linacs and with reactors. List of radioactive isotopes used in medicine for treatment and for producing images includes more than 100 nuclei with life time from several years, e.g. 60Co, to several seconds, e.g. 191mIr.
Photonuclear reactions offer another way for isotope production. Electron accelerator is several times cheaper than cyclotron
PET isotopes – short living isotopes for positron emission tomography 11C (20.4 min), 13N (10.0 min), 15O (2.0 min), 18F (109.8 min)
can be produced via (γ,n) reaction on target nuclei 12C, 14N, 16O, 19F
Cross section of (γ,n) reaction is 10-100 lower than cross section of reactions with heavy charged particles obtained with cyclotron. However for photonuclear reactions much more thick target can be used, so total isotope yield can be sufficiently high.
Estimations for PET isotopes yields with cyclotron and RTM Isotope
Accelerator
Reaction
Target
Saturation Yields
11C
70/35 MeV RTM
12C(γ,n)11C
Graphite -- Diamond
2.6/3.9 Ci -- 4.8/7.1 Ci
11 MeV Cyclotron
14N(p,α)11C
N2 / 0.5-1% O2
3.0 Ci
70/35 MeV RTM
14N(γ,n)13N
Melamine (C3H3N3)
1.2/1.6 Ci
11 MeV Cyclotron
16O(p,α)13N
5mM Water&Ethanol
100 mCi
70/35 MeV RTM
16O(γ,n)15O
Water
3.2/2.5 Ci
11 MeV Cyclotron
15N(p,n)15O
N2 / 2.5% O2
760 mCi
70/35 MeV RTM
19F(γ,n)18F
Perfluorocarbon or SF6 gas
2.2/3.0 Ci
11 MeV Cyclotron
18O(p,n)18F
H218O or18O2
1-3 Ci
13N
15O
18F
Radiochemistry can not be applied for (γ,n) reaction products – isotope with the same as target chemical properties is produced. How to extract? For example, use of thin powder and pick-up recoil nuclei with gas stream.
99mTc
(the daughter nucleus of 99Mo) is most used isotope in medical imagine. It is now obtained with nuclear reactor. Can be obtained in 100Mo(γ,n)99Mo reaction. Method was experimentally verified. Production of very pure 123I was demonstrated with electron accelerators at several centers. Reaction 124Xe (γ,n)123Xe123I was used. Electron accelerator for medical isotopes production: Beam energy from ~ 25 MeV to ~40 MeV Beam average current from ~100 µA to ~200 µA Conversion to bremsstrahlung X-rays
Explosive detection with photonuclear reactions Original idea of L. Alvarez Tested by Trower W.P., NIM B79 (1993) 589 The most effective method of concealed explosive search till now is odorant method - dogs. However explosive can be detected by detecting its main constituents - nitrogen and oxygen. Anomaly concentration of nitrogen and oxygen in certain proportion means high probability of explosive presence.
β decaying radionuclei photoproduced on stable isotopes with abundance >1 % resulting in three or fewer nucleons.
Only photonuclear reactions on carbon, nitrogen and oxygen for beam energy below 70 MeV can produce residual nuclei with half life between 10 and 100 ms.
Explosive detection with photonuclear reactions Lebedev Institute Max 70 MeV electron accelerator
Detector
Scanned electron beam
Moving object
Explosive detection steps 1. Irradiate during 5-10 µs specific portion of object by X-ray radiation generated by electron beam at large (~object dimensions) bremsstrahlung target. 2. Get decay curve within ~ 10-20 ms by mean of registration of secondary X-rays, produced by positrons, emitted by residual nuclei. 3. Go to the next part of object Irradiation of the same object part with different electron energy can be used to distinguish between C, N and O. For the same goal different secondary X-rays registration threshold energy can be used.
Decay curves measured for different substances
Melamine
Room air
Example of explosive detection
No explosive
Semtex, 125 g
Electron accelerator for explosive detection technique: Beam energy from ~25 to ~70 MeV Pulsed current ~20-50 mA Pulse duration ~5-10 µs Pulse repetition rate 10-50 Hz Conversion to bremsstrahlung X-rays
SINP MSU experience in design, construction and application of electron accelerators for activation analysis, isotopes production and explosive detection
SINP MSU 70 MeV PULSED RACE TRACK MICROTRON WITH RARE-EARTH PERMANENT MAGNETS
Innovations: -large ~1 T rare-earth permanent end magnets - rectangular accelerating structure with RF quadrupole focusing - electron beam phase shifter - rare-earth permanent magnet compact quadrupole triplets - self excitation RF system
Injection energy
48 keV
Energy gain
4.8 MeV / orbit
Orbits
14
Output energy
14.8 - 68.3 MeV
Output current at 68.3 MeV
10 mA
Orbit circumference increase
1λ/orbit
Operating frequency
2,856 MHz
Klystron power pulsed
6 MW
End magnet field induction
0.963 T
RTM dimensions
2.2x1.8x0.9 m3
A 70 Mev racetrack microtron, V.I. Shvedunov, A.N. Ermakov, I.V. Gribov, E.A. Knapp, G.A. Novikov, N.I. Pakhomov, I.V. Shvedunov, V.S. Skachkov, N.P. Sobenin, W.P. Trower and V.R. Yajlijan, Nucl. Instrum. Meth. A550 (2005)39-53
Photoactivation technique Gamma rays spectrum from Ge detector after irradiation of 197Au with bremsstrahlung from 70 MeV RTM
55 MeV PULSED RACE TRACK MICROTRON AT SINP MSU WITH EXPLOSIVE DETECTION SYSTEM – COLLABORATION WITH LEBEDEV PHYSICAL INSTITUTE
Synchrotron radiation from orbits
Radiation therapy Use of ionizing radiation to kill tumor cells by destroying DNA via complicated physical, chemical and biological processes. Together with tumor cells normal cells on the way of radiation are also killed. Special tactic of irradiation: irradiation from several sides, using special collimators, intraoperative radiation therapy etc.
Cell survival curves
Typical cell survival curves for high LET (densely ionizing) radiation and low LET (sparsely ionizing) radiation. LET – linear energy transfer
Comparison of electrons and X-rays dose-depth dependencies
PPD – percentage depth dose
External X-ray radiation therapy Irradiation by bremsstrahlung radiation produced by 1 - 25 MeV electron beam at special target.
External electron radiation therapy Irradiation by 25 - 50 MeV electron beam scattered by foil via special applicator.
Scanditronix medical RTM MM-50
Stereotactic radiation surgery (SRS) Providing of high dose of X-rays radiation to well localized volume using several radiation sources or single easy movable source. SRS uses dedicated miniature electron accelerator with energy 4-6 MeV, fixed at robotic arm.
CyberKnife - based on 6 MeV X-band linac
Intraoperative radiation therapy (IORT) Providing of high dose to well localized volume using several radiation sources or single easy movable source. Similar to IORT modern SRS uses dedicated miniature electron accelerator with energy 4-6 MeV, fixed at robotic arm.
Betatron Russia
Mobetron USA
Novac7 Italy
Liac Italy
UPC-SINP MSU-CIEMAT collaboration for IORT dedicated 12 MeV race-track microtron
Conclusion Electron beams in the energy range 0.5 – 100 MeV have wide and growing spectrum of applications. There are three distinctly different kind of commercial activity in this field : -accelerator design and construction; -technology development; -facility construction and technology application. Many labs conduct R&D in accelerator physics and only a few private companies manufacture commercial electron accelerators. New accelerator busyness can be successful only with new ideas in accelerator design and application.
